Ethylene-styrene interpolymers blends

Disclosed are ethylene-vinyl acetate/ethylene-styrene interpolymer blends, which are useful in preparing foams exhibiting improved compression set resistance, dimensional stability and rebound resilience at similar foam densities than known foam systems, e.g. EVA. The crosslinked foams are particularly useful in fabricating footwear and gaskets. 

Blends of LDPE with ethylene styrene interpolymers (ESI, see Section 3.2) also have a complex microstructure. The semi-crystalline LDPE is immiscible with the amorphous ESI, which has a glass transition temperature (Tg) just above room temperature. Consequently there are rigid crystalline regions and rubbery amorphous LDPE, mixed on a 0.1 pm scale, together with regions of leathery ESI on a 5 to 10 pm scale (71). 

There have been more efforts to use blends such as Nova Chemicals Arcel (an ethylene styrene interpolymer in bead form) to create a more durable foam than EPS. EPP can be moulded into complex shapes, with the steam bonding of the beads (291). These packaging foams compete with polyolefin film products such as Jiffy foam (bubblewrap) and macrobubbles made by heat sealing 150 mm lengths of tubular LDPE film. As it is difficult or costly to recycle such foam products, in some countries there is a move towards biodegradable starch foams and moulded paperboard. 

Foams were prepared from blends of EVA and ethylene-styrene interpolymers having styrene contents ranging from 30 to 73 wt.% and Tgs ranging from -2 to 33C, in the presence of various amounts of dicumyl peroxide and their viscoelastic and mechanical properties investigated. The effects of styrene content and peroxide concentration on the morphology, degree of crosslinking and expansion ratio of the foams were assessed as was the influence of the type of ethylene-styrene interpolymer on the Tg of the foams. It was found that the Tg of the blends could be tailored by selection of the appropriate interpolymer. 19 refs. 

ETHYLENE-STYRENE INTERPOLYMER FOAM BLENDS MECHANICAL PROPERTIES AND SPORT APPLICATIONS... 

Foamed blends of ethylene-styrene interpolymer and LDPE were subjected to a range of mechanical tests, including compressive impact testing, Instron compression and Poisson s ratio measurements, compressive creep measurements and compression set and recovery measurements. The data obtained were compared with those for EVA and the suitability of these foamed blends as replacements for EVA in the manufacture of soccer shin guards and midsoles for sports shoes was evaluated. 20 refs. 

Foams 2000 Second International Conference on Thermoplastic Foam. Conference proceedings. Parsippany, N.J., 24th-25th October 2000, p. 102-7 NEW PRODUCTS MADE FROM ETHYLENE-STYRENE INTERPOLYMER/LDPE BLEND FOAMS FOR VARIOUS APPLICATIONS Ramesh N S Sealed Air Corp. 

Ethylene-styrene interpolymers (ESI) exhibit some interesting properties when they are blended with LLDPE or PP. Aspects covered include foaming technology, blend... 

Patent Number US 6111020 A1 20000829 CROSSLINKED FOAMS FROM BLENDS OF ETHYLENE VINYL ACETATE AND ETHYLENE-STYRENE INTERPOLYMERS... 

BLENDS OF ETHYLENE-STYRENE INTERPOLYMERS MISCIBILITY CONSIDERATIONS... 

In the last few years, some new materials have emerged as base materials for CPOF [17,18]. Examples are ethylene-styrene interpolymers, metallocene polyethylenes, polypropylene foams, and blends of different POs. 

Since the early 1990s, the constrained geometry metallocene catalysts have been used by Dow to produce either alternating or pseudo-random ethylene-co-styrene interpolymers (ESI) (Stevens et al. 1991). ESI with up to 50 wt% styrene is semicrystalline it is known to compatibilized PE/PS blends since it forms domain structures into which the homopolymers can dissolve. ESI also has good melt strength, mechanical, impact, and damping characteristics (Ellebrach and Chum 1998). Flow and processing information on ESI were pubUshed (Karjala et al. 1998). 

As reported by Diehl et al. [58], interpolymers are also compatible with a broader range of polymers, including styrene block copolymers [59], poly(vinyl chloride) (PVC)-based polymers [60], poly(phenylene ethers) [61] and olefinic polymers such as ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer and chlorinated polyethylene. Owing to their unique molecular structure, specific ESI have been demonstrated as effective blend compatibilizers for polystyrene-polyethylene blends [62,63]. The development of the miscibility/ compatibility behavior of ESI-ESI blends differing in styrene content will be highlighted below. 

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